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Improve write performance, avoid roundtrip per fragment

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This commit is contained in:
Lucian Petrut
2026-09-07 15:18:21 +00:00
parent f18a8d3d71
commit 0039fdbb3d
3 changed files with 99 additions and 118 deletions
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docs/reverse_engineering_procedure.md
+7 -7
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@@ -248,13 +248,13 @@ the ticket switched from `NfcGetVmFiles` to `NfcRandomAccessOpenDisk`
`NfcRandomAccessOpenDisk`). Integration tests create a temporary empty
10 GiB VM for the run so writes cannot land on other lab disks.
The Python client splits writes larger than 64 KiB into AIO chunks and
keeps four in flight (VDDK's `NfcAioInitSession` buffer count). Larger
windows were tried; they do not match VDDK throughput. Header and extra
go in one `sendall`, with `TCP_NODELAY`. Details:
`docs/nfc_write.md`. Proof: write then read in
`tests/integration/test_nfc_read_write.py` and the VDDK cross-check in
`tests/integration/test_crosscheck.py`.
A write larger than 64 KiB is one AIO `opId` with several type-7
request fragments (same layout as read *replies*: total length, then
fragment offset / length) and a single 44-byte ACK. Separate
`VixDiskLib_Write` calls are not coalesced. Header and extra go in one
`sendall`, with `TCP_NODELAY`. Details: `docs/nfc_write.md`. Proof:
write then read in `tests/integration/test_nfc_read_write.py` and the
VDDK cross-check in `tests/integration/test_crosscheck.py`.
## Step 11 — NBDSSL: second TLS after `PROXY vpxa-nfcssl`